code.kt

// get all entities
val ids = world.aspectSubscriptionManager
    .get(Aspect.all())

// save as raw json string - for demo purposes 
val saved = StringWriter().use { sw ->
    serializer.save(sw, SaveFileFormat(ids))
    sw.toString()
}

// process json; resolve type mappings, referenced components etc
val context = Context(saved.toJson()) // "some_prefab.json"

// SomePrefab.java
val source: String = generatePrefab("SomePrefab", context)

some_prefab.json

{
	"metadata": {
		"version": 1
	},
	"componentIdentifiers": {
		"com.artemis.component.ComponentY": "ComponentY",
		"com.artemis.component.PrimitiveComponent": "PrimitiveComponent",
		"com.artemis.component.CompB": "CompB",
		"com.artemis.component.CompA": "CompA",
		"com.artemis.component.ComponentX": "ComponentX",
		"com.artemis.component.PositionXy": "PositionXy",
		"com.artemis.component.CompC": "CompC"
	},
	"entities": {
		"0": {
			"archetype": 5,
			"components": {
				"ComponentX": {
					"text": "hell, comp x"
				},
				"ComponentY": {
					"text": "comp y, also text"
				},
				"PositionXy": {
					"xy": {
						"x": 1,
						"y": 2
					}
				},
				"PrimitiveComponent": {
					"aInt": 123,
					"aDouble": 4
				}
			}
		},
		"1": {
			"archetype": 9,
			"components": {
				"CompA": {
					"a": 13300
				},
				"CompB": {
					"b": 300
				},
				"CompC": {
					"c": 40
				},
				"ComponentX": {
					"text": "foo"
				},
				"ComponentY": {
					"text": "bar"
				},
				"PositionXy": {
					"xy": {
						"x": 231,
						"y": -2
					}
				},
				"PrimitiveComponent": {
					"aInt": 123,
					"aDouble": 4
				}
			}
		}
	},
	"archetypes": {
		"5": [
			"PositionXy",
			"ComponentX",
			"ComponentY",
			"CompC",
			"PrimitiveComponent"
		],
		"9": [
			"PositionXy",
			"ComponentX",
			"ComponentY",
			"CompC",
			"PrimitiveComponent",
			"CompA",
			"CompB"
		]
	}
}

SomePrefab.java

package com.artemis.generated;

import com.artemis.ComponentMapper;
import com.artemis.EntityTransmuter;
import com.artemis.World;
import com.artemis.annotations.AspectDescriptor;
import com.artemis.component.CompA;
import com.artemis.component.CompB;
import com.artemis.component.CompC;
import com.artemis.component.ComponentX;
import com.artemis.component.ComponentY;
import com.artemis.component.PositionXy;
import com.artemis.component.PrimitiveComponent;
import com.artemis.io.EntityPoolFactory;
import com.artemis.prefab.CompiledPrefab;

public final class SomePrefab extends CompiledPrefab {
	@AspectDescriptor(
			all = {PositionXy.class, ComponentX.class, ComponentY.class, CompC.class, PrimitiveComponent.class}
	)
	private EntityTransmuter transmuter5;

	@AspectDescriptor(
			all = {PositionXy.class, ComponentX.class, ComponentY.class, CompC.class, PrimitiveComponent.class, CompA.class, CompB.class}
	)
	private EntityTransmuter transmuter9;

	private ComponentMapper<CompA> compAMapper;

	private ComponentMapper<CompB> compBMapper;

	private ComponentMapper<CompC> compCMapper;

	private ComponentMapper<ComponentX> componentXMapper;

	private ComponentMapper<ComponentY> componentYMapper;

	private ComponentMapper<PositionXy> positionXyMapper;

	private ComponentMapper<PrimitiveComponent> primitiveComponentMapper;

	public void compiledCreate(World world) {
		EntityPoolFactory factory = entityFactory(world, 2);

		// creating entity 0
		int e0 = factory.createEntityId();
		transmuter5.transmute(e0);
		{
			ComponentX c = componentXMapper.get(e0);
			c.text = "hell, comp x";
		}
		{
			ComponentY c = componentYMapper.get(e0);
			c.text = "comp y, also text";
		}
		{
			PositionXy c = positionXyMapper.get(e0);
			Vector2 xy = c.xy;
			xy.x = 1.0f;
			xy.y = 2.0f;
		}
		{
			PrimitiveComponent c = primitiveComponentMapper.get(e0);
			c.aInt = 123;
			c.aDouble = 4.0;
		}

		// creating entity 1
		int e1 = factory.createEntityId();
		transmuter9.transmute(e1);
		{
			CompA c = compAMapper.get(e1);
			c.a = 13300;
		}
		{
			CompB c = compBMapper.get(e1);
			c.b = 300.0f;
		}
		{
			CompC c = compCMapper.get(e1);
			c.c = 40;
		}
		{
			ComponentX c = componentXMapper.get(e1);
			c.text = "foo";
		}
		{
			ComponentY c = componentYMapper.get(e1);
			c.text = "bar";
		}
		{
			PositionXy c = positionXyMapper.get(e1);
			Vector2 xy = c.xy;
			xy.x = 231.0f;
			xy.y = -2.0f;
		}
		{
			PrimitiveComponent c = primitiveComponentMapper.get(e1);
			c.aInt = 123;
			c.aDouble = 4.0;
		}

	}
}